Menus Subscribe Search

Follow us


Hey TSA, Racial Profiling Doesn’t Work

• November 30, 2010 • 3:34 PM

Looking at the math behind profiling meant to nab terrorists, computer scientist William Press realized it may be less effective than purely random sampling.

Arguments over racial profiling at the airport security line typically turn around the assumption that such screening, at least to some extent, works. The idea may be unsavory, but it sounds logical: If we target people with a higher probability of being terrorists — whether they have Saudi passports, beards or headscarves — we’d have a better chance of catching real terrorists in the process.

The question becomes one of morals. Is this the right thing to do? Does the societal benefit (catching more terrorists) outweigh the cost (compromising our ethics)?

William Press, a professor of computer science and integrative biology at the University of Texas at Austin, now realizes we don’t have to weigh this dilemma at all. Racial profiling, he has concluded, simply doesn’t work. Never mind how you feel about it. The math doesn’t add up.

Plucking out of line most of the vaguely Middle Eastern-looking men at the airport for heightened screening is no more effective at catching terrorists than randomly sampling everyone. It may even be less effective.

Press stumbled across this counterintuitive concept — sometimes the best way to find something is not to weight it by probability — in the unrelated context of computational biology. The parallels to airport security struck him when a friend mentioned he was constantly being pulled out of line at the airport.

“He’s not on any do-not-fly list, and it occurred to me it was exactly this phenomenon,” Press said. “Either explicitly or implicitly, there was some kind of profiling going on, and the same innocent individual was being screened over and over again. That draws resources away from the screening that  would find the bad guy. I realized those were basically the same problems.”

Racial profiling, in other words, doesn’t work because it devotes heightened resources to innocent people — and then devotes those resources to them repeatedly even after they’ve been cleared as innocent the first time. The actual terrorists, meanwhile, may sneak through while Transportation Security Administration agents are focusing their limited attention on the wrong passengers.

[class name="dont_print_this"]

Idea Lobby

THE IDEA LOBBY
Miller-McCune's Washington correspondent Emily Badger follows the ideas informing, explaining and influencing government, from the local think tank circuit to academic research that shapes D.C. policy from afar.

[/class] Press tested the theory in a series of probability equations (the ambitious can check his math here and here).

“I was flabbergasted,” he said.

Sampling based on profiling is mathematically no more effective than uniform random sampling. The optimal equation, rather, turns out to be something called “square-root sampling,” a compromise between the other two methods.

“Crudely,” Press writes of his findings in the journal Significance, if certain people are “nine times as likely to be the terrorist, we pull out only three times as many of them for special checks. Surprisingly, and bizarrely, this turns out to be the most efficient way of catching the terrorist.”

This model minimizes the overemphasis on people like Press’ friend, creating the best trade-off between over- and under-screening profiled passengers.

“It’s just a little piece of math,” Press said, “that somehow has escaped the textbooks because you don’t need it very often.”

Square-root sampling, though, still represents a kind of profiling, and, Press adds, not one that could be realistically implemented at airports today. Square-root sampling only works if the profile probabilities are accurate in the first place — if we are able to say with mathematical certainty that some types of people are “nine times as likely to be the terrorist” compared to others. TSA agents in a crowded holiday terminal making snap judgments about facial hair would be far from this standard.

“The nice thing about uniform sampling is there’s nothing to be inaccurate about, you don’t need any data, it never can be worse than you expect,” Press said. “As soon as you use profile probabilities, if the profile probabilities are just wrong, then the strong profiling just does worse than the random sampling.”

Press would like to see policymakers get behind this conclusion, even if they can’t follow along with his algorithms.

“They don’t have to look at the details of the math,” he said. “I think that, when you come down to it, there’s an alternative that avoids the political minefield and is consistent with democratic values and is relatively easy to do.”

Randomly sample everyone.

Subscribe to Miller-McCune

Emily Badger
Emily Badger is a freelance writer living in the Washington, D.C. area who has contributed to The New York Times, International Herald Tribune and The Christian Science Monitor. She previously covered college sports for the Orlando Sentinel and lived and reported in France.

More From Emily Badger

A weekly roundup of the best of Pacific Standard and PSmag.com, delivered straight to your inbox.

Recent Posts

September 29 • 1:21 PM

Conference Call: Free Will Conference


September 29 • 12:00 PM

How Copyright Law Protects Art From Criticism

A case for allowing the copyright on Gone With the Wind to expire.


September 29 • 10:00 AM

Should We Be Told Who Funds Political Attack Ads?

On the value of campaign finance disclosure.


September 29 • 8:00 AM

Searching for a Man Named Penis

A quest to track down a real Penis proves difficult.


September 29 • 6:00 AM

Why Do So Many People Watch HGTV?

The same reason so many people watch NCIS or Law and Order: It’s all a procedural.


September 29 • 4:00 AM

The Link Between Depression and Terrorism

A new study from the United Kingdom finds a connection between depression and radicalization.


September 26 • 4:00 PM

Fast Track to a Spill?

Oil pipeline projects across America are speeding forward without environmental review.


September 26 • 2:00 PM

Why Liberals Love the Disease Theory of Addiction, by a Liberal Who Hates It

The disease model is convenient to liberals because it spares them having to say negative things about poor communities. But this conception of addiction harms the very people we wish to help.


September 26 • 1:21 PM

Race, Trust, and Split-Second Judgments


September 26 • 9:47 AM

Dopamine Might Be Behind Impulsive Behavior

A monkey study suggests the brain chemical makes what’s new and different more attractive.


September 26 • 8:00 AM

A Letter Becomes a Book Becomes a Play

Sarah Ruhl’s Dear Elizabeth: A Play in Letters From Elizabeth Bishop to Robert Lowell and Back Again takes 900 pages of correspondence between the two poets and turns them into an on-stage performance.


September 26 • 7:00 AM

Sonic Hedgehog, DICER, and the Problem With Naming Genes

Wait, why is there a Pokemon gene?


September 26 • 6:00 AM

Sounds Like the Blues

At a music-licensing firm, any situation can become nostalgic, romantic, or adventurous, given the right background sounds.


September 26 • 5:00 AM

The Dark Side of Empathy

New research finds the much-lauded feeling of identification with another person’s emotions can lead to unwarranted aggressive behavior.



September 25 • 4:00 PM

Forging a New Path: Working to Build the Perfect Wildlife Corridor

When it comes to designing wildlife corridors, our most brilliant analytical minds are still no match for Mother Nature. But we’re getting there.


September 25 • 2:00 PM

Fashion as a Inescapable Institution

Like it or not, fashion is an institution because we can no longer feasibly make our own clothes.


September 25 • 12:00 PM

The Fake Birth Mothers Who Bilk Couples Out of Their Cash by Promising Future Babies

Another group that’s especially vulnerable to scams and fraud is that made up of those who are desperate to adopt a child.


September 25 • 10:03 AM

The Way We QuickType


September 25 • 10:00 AM

There’s a Name for Why You Feel Obligated to Upgrade All of Your Furniture to Match

And it’s called the Diderot effect.


September 25 • 9:19 AM

School Counselors Do More Than You’d Think

Adding just one counselor to a school has an enormous impact on discipline and test scores, according to a new study.


September 25 • 9:05 AM

Sponsors: Coming to a Sports Jersey Near You

And really, it’s not that big of a deal.


September 25 • 8:00 AM

The Most Pointless Ferry in Maryland

Most of the some 200 ferries that operate in the United States serve a specific, essential purpose—but not the one that runs across the Tred Avon River.


September 25 • 7:00 AM

Hating Happiness

People all over the world are afraid of happiness, and that’s not necessarily a bad thing. It’s yet another challenge to the notion that positive thinking can heal all wounds.


September 25 • 6:00 AM

Why I’m No Longer Willing to Give My Money to the NRA

I grew up with guns—as a kid and during my 20-year military career—and support individual ownership rights, but the National Rifle Association’s platform has shifted radically in recent years.


Follow us


Dopamine Might Be Behind Impulsive Behavior

A monkey study suggests the brain chemical makes what's new and different more attractive.

School Counselors Do More Than You’d Think

Adding just one counselor to a school has an enormous impact on discipline and test scores, according to a new study.

How a Second Language Trains Your Brain for Math

Second languages strengthen the brain's executive control circuits, with benefits beyond words.

Would You Rather Go Blind or Lose Your Mind?

Americans consistently fear blindness, but how they compare it to other ailments varies across racial lines.

On the Hunt for Fake Facebook Likes

A new study finds ways to uncover Facebook Like farms.

The Big One

One company, Amazon, controls 67 percent of the e-book market in the United States—down from 90 percent five years ago. September/October 2014 new-big-one-5

Copyright © 2014 by Pacific Standard and The Miller-McCune Center for Research, Media, and Public Policy. All Rights Reserved.